It’s been 74 years since the wreckage of the Pan Am plane that revolutionized aviation safety.

The wreckage was discovered 74 years after a Pan American Airways plane went down in the Atlantic Ocean, a crash that mandated the airline’s safety specifications.

The Clipper Endeavor was found 2,000ft (610m) below sea level off the coast of Puerto Rico by a sonar-equipped drone. It went down on April 11, 1952 following a multi-engine failure shortly after takeoff.

All on board survived the crash – but passengers struggled to find life jackets and rafts as the plane sank quickly. Of the 69 passengers and crew on board, only 17 survived.

The disaster prompted sweeping reforms in aviation security, including mandatory pre-flight safety briefings on every commercial flight.

The expedition to find the wreck was led by the Air/Sea Heritage Foundation in partnership with the Discovery Channel’s Expedition Unknown show and several other organizations.

Last month, explorers located the wreckage of the Douglas DC-4 using an autonomous sonar drone and found the wreckage and tail of the plane.

Russ Matthews, president of the Air/Sea Heritage Foundation, said: “We are all surprised and delighted by this discovery.

The plane was carrying 64 passengers and five crew members on its way to New York when the pilot was forced to land due to heavy rain.

The resulting confusion has been a “motivator” for modern regulations mandating better flotation devices on airplanes and pre-flight briefings on their use, aviation safety expert John Cox told the AP.